The Gold Standard, and only way, to ascertain which foods cause adverse reactions, is by accurately recording the times and duration of all symptoms, illness or stress, as well as everything you eat and drink. This includes all prescribed medicines and other supplements, all sweets, nibbles and even licking out the mixing bowl when cooking!
This record diary should be continued for 2 weeks and should be representative of your normal diet. Use a new page each day. Ideally, it should be analysed by a registered dietician or nurse with nutritional training.
It is helpful to keep food packaging for reference by the health professional.